Safety set-screw.



Patented Dec. 30, 1913.

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JAMES H. GRAHAM, OF TORRINGTON, CONNECTICUT, ASSIGNOR TO THE STANDARD COMPANY, OF TORRINGTON, CONNECTICUT,

A CORPORATION OF MAINE.

SAFETY SET-SCREW.

Specification of Letters Patent.

Patented Dec. 30, 1913..

To all whom it may concern:

Be it known that I, JAMES H. GRAHAM, a citizen of the United States, residing at Torrington, in the county of Litchfield, State of Connecticut, have invented certain new and useful Improvements in Safety Set- Screws, of which the following is a description, reference being had to the accompanying drawing and to the letters and figures of reference marked thereon.

My invention relates to improvements in so-called safety setscrews, which are embedded screws used for example to hold collars and pulleys on shafts and the like, leaving no projection and allowing convenient removal whenever it is desired to do so. The invention is in a sense designed as an improvement on the safety set screw shown in Patent No. 869,086, issued October 22d, 1907, to Clemence E. Hoffman, and consists of novel features and combinations of the same, all as hereinafter described and referred to in the appended claim.

The invention is illustrated in the accompanying drawings, in which,

Figure 1 is a sectional side elevation of my invention as applied for fastening a collar on a shaft; Fig. 2 is a sectional view of the set screw showing three different forms of the point, viz., cupped, fiat and oval; Fig. 3 is a detail View of the wrench; and Fig. 4 is a sectional View like Fig. 1, showing the wrench applied to the safety set screw.

In these drawings, the safety set screw itself is illustrated by 1. It has an external screw thread 2, and is formed with a socket having two internal screw threads running in opposite directions. While the set screw may have a longitudinal opening extending entirely through it instead of the socket, the latter form is preferable, and the lower end of said socket, or end adjacent where the-end of the wrench comes, is cupped, as shown at 3, in effect forming a shoulder or seat 4, so that only a minimum frictional contact of shown at 7, s0

the seat in the the inner end of end of the socket takes place, thus preventing interlocking of the wrench with the set screw. By this arrangement, no matter how great a strain is applied to the wrench to manipulate the safety set screw in or out, very slight pressure only is necessary to release the wrench from the screw. The wrench is illustrated by 4:, and comprises the squared central portion 5, adapted for the ready attachment of a wrench or other tool, its end portions Gbeing threaded reversely to each other and of a pitch corresponding to the pitch of the internal screw threads of the socket, which pitch is greater than that of the external thread 2. The outer ends of the wrench are rounded, as as to minimize the frictional the ends of the wrench with socket.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent, is

The combination of a safety set screw provided with an external screw thread and a socket having right and left hand screw threads of greater pitch than the external screw thread and having a seat at the lower end closing said socket and forming a bear ing end for the set screw, and a wrench having a central portion for engagement of a tool and having oppositely extending portions with right and left hand threads, respectively, for engagement with the internal screw threads of the socket, said extending portions being of sufficient length to permit the ends thereof to engage the closed end of the socket.

In testimony whereof I affix my signature. in presence of two witnesses.

JAMES H. GRAHAM.

engagement of Vitnesses:

E. J. MILLs, W. C. Rown.

the wrench with the inner 

